提交 2e758910 编写于 作者: P Peter Hurley 提交者: Greg Kroah-Hartman

serial: core: Flush ldisc after dropping port mutex in uart_close()

The tty buffers (and any line discipline buffers) must be flushed after
the UART hardware has shutdown; otherwise, a racing open on the same
tty may receive data from the previous session, which is a security
hazard. However, holding the port mutex while flushing the line
discipline buffers creates a lock inversion if the set_termios()
handler takes the port mutex (as it does in the followup patch,
'serial: Fix locking for uart driver set_termios method'.

Flush the ldisc buffers after dropping the port mutex; the tty lock
is still held which prevents a concurrent open() from advancing while
flushing. Since no new rx data is possible after uart_shutdown() until
a new open reinitializes the port, the later flush has no impact on
what data is being discarded.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
上级 479e9b94
...@@ -1361,9 +1361,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp) ...@@ -1361,9 +1361,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
mutex_lock(&port->mutex); mutex_lock(&port->mutex);
uart_shutdown(tty, state); uart_shutdown(tty, state);
tty_ldisc_flush(tty);
tty_port_tty_set(port, NULL); tty_port_tty_set(port, NULL);
tty->closing = 0; tty->closing = 0;
spin_lock_irqsave(&port->lock, flags); spin_lock_irqsave(&port->lock, flags);
...@@ -1390,6 +1387,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp) ...@@ -1390,6 +1387,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
wake_up_interruptible(&port->close_wait); wake_up_interruptible(&port->close_wait);
mutex_unlock(&port->mutex); mutex_unlock(&port->mutex);
tty_ldisc_flush(tty);
} }
static void uart_wait_until_sent(struct tty_struct *tty, int timeout) static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册